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Struct reader Amanuensis

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©1996-2017 Roedy Green of Canadian Mind Products

Disclaimer

This essay does not describe an existing computer program, just one that should exist. This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have prepared to help you is right here.

This project outline is not like the artificial, tidy little problems you are spoon-fed in school, when all the facts you need are included, nothing extraneous is mentioned, the answer is fully specified, along with hints to nudge you toward a single expected canonical solution. This project is much more like the real world of messy problems where it is up to you to fully the define the end point, or a series of ever more difficult versions of this project and research the information yourself to solve them.

Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; or give you any additional materials. I have too many other projects of my own.

Though I am a programmer by profession, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project in any way you please and to keep all the profits from your endeavour.

Please do not email me about this project without reading the disclaimer above.

This is one of the amanuensis projects. Another boring task is writing code to read and write C structures using LEDataInputStream and DataInputStream. See the File I/O Amanuensis for the general idea. You would either:
  1. Feed it a C/C++ declaration, analyse it with a parser (see parser in the glossary) and have it generate a set of Java source code class declarations and the read and write method to read one struct.
  2. Check off the types and names of the various fields in a dialog box, creating a binary record descriptor. Use this to generate a C++ struct source code and the set of Java source code class declarations and the read and write method to read one struct.
  3. Use reflection to discover the structure of the Java class which may have embedded references. You need to create a fixed length record, so you must presume each reference field is not null and you also need caps on the lengths of String fields.
Even if you can’t get it perfect and just throw up your hands at the problem of references and variable length Strings, you can still save a lot of the bullwork. You can always manually touch up the crude source code you generate.

A more efficient variant would generate code to read entire records into a byte array, then generate get/put accessor functions to read/write the various fields. The accessor would have to construct the binary value by shift and logical or of the bytes at the corresponding offsets in the byte array, using logic similar to that in LEDataInputStream and LEDataOutputStream.

LeDataStream
Reading C Structs

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